Aggregates of mineral fibers and thermoplastic materials useful particularly as underlayers for structural sheathings for acoustic insulation

ABSTRACT

The production of structural sheathings or facings having an underlayer affixed thereto, to serve as an acoustical insulating structural member, said underlayer being formed by the combination of mineral fibers, particularly glass fibers of relatively long length in interlaced condition, which is permeated with thermoplastic compositions comprising mixtures of one or more elastomers such as natural or artificial latex, and one or more adjuvants for promoting a chemical bond between the mineral fibers and elastomer component. This underlayer is prepared by forming a mat by the deposition of the mineral fibers in successive layers, which is followed by the thorough impregnation of the fibers with an aqueous dispersion of said thermoplastic composition, the withdrawal of the excess of the latter from the impregnated mat, and the drying of the mat and the final heating thereof to attain an effective reticulation of plastic composition amongst the glass fibers before the mat is accumulated on a storage roller. The final production step of gluing of the underlayers to a sheathing or other support is rendered more secure and satisfactory by partially or completely clogging the pores at one or both faces of the underlayer with a special filling layer before the glue is applied thereto. Furthermore, the appearance of the underlayer on its support is improved, especially when the latter is a vinyl plastic, by removing the folds therefrom which are caused by the rolling up of the former on a reel in the course of its preparation. The elimination of these folds is attained by heating the mat immediately prior to its fixing on its support to relieve slightly the binding of the layers of fibers by the thermoplastic material, which gives rise to a re-arrangement of the stratification of fibers adjacent to the surfaces of the underlayer.

United States Patent J umentier et al.

3,658,633 Apr. 25, 1972 [54] AGGREGATES OF MINERAL FIBERS AND THERMOPLASTIC MATERIALS USEFUL PARTICULARLY AS UNDERLAYERS FOR STRUCTURAL SHEATHINGS FOR ACOUSTIC INSULATION [72] inventors: Claude Jumentier, La Celle Saint Cloud; Alain Bonnet, Clermont; Claude Bolteau, Nogent sur Oise, all of France [73] Assignee: Compagnle De Saint-Cobain, Neuilly-sur- Seine (Seine), France [22] Filed: July 25, 1968 [21] Appl. No.: 747,583

[30] Foreign Application Priority Date Aug. 8, 1967 France ..1 17218 [52] U.S.Cl ..16l/l56,l56/62.4,156/377,

161/158,161/162,l61/168,161/170,181/33 GA [51] Int. Cl. ..B32b 17/00, B32b 19/00 [58] Field ofSearch ..16l/152, 156, 158, 162, 168,

[56] References Cited UNITED STATES PATENTS 1,503,605 8/1924 Shaw ..l6l/l52 2,285,423 6/1942 Esser ..l61/152 2,666,699 1/1954 McQuiston et al. .....l6l/l58 3,121,656 2/1964 Giuck ..161/158 3,137,589 6/1964 Reinhard et al. .....i6l/l70 3,509,012 4/1970 Marzocci ..16l/l70 3.513.065 5/1970 Pearson ..I6l/l5l Primary Examiner-Robert F. Burnett Assistant Examiner-Raymond O. Linker, .lr. Attorney-Samuel Lebowitz, Dale A. Bauer, John L. Seymour and Bauer and Seymour [5 7] ABSTRACT The production of structural sheathings or facings having an underlayer affixed thereto, to serve as an acoustical insulating structural member, said underlayer being formed by the combination of mineral fibers, particularly glass fibers of relatively long length in interlaced condition, which is permeated with thermoplastic compositions comprising mixtures of one or more elastomers such as natural or artificial latex, and one or more adjuvants for promoting a chemical bond between the mineral fibers and elastomer component. This underlayer is prepared by forming a mat by the deposition of the mineral fibers in successive layers, which is followed by the thorough impregnation of the fibers with an aqueous dispersion of said thermoplastic composition, the withdrawal of the excess of the latter from the impregnated mat, and the drying of the mat and the final heating thereof to attain an effective reticulation of plastic composition amongst the glass fibers before the mat is accumulated on a storage roller. The final production step of gluing of the underlayers to a sheathing or other support is rendered more secure and satisfactory by partially or completely clogging the pores at one or both faces of the underlayer with a special filling layer before the glue is applied thereto. Furthermore, the appearance of the underlayer on its support is improved, especially when the latter is a vinyl plastic, by removing the folds therefrom which are caused by the rolling up of the former on a reel in the course of its preparation. The elimination of these folds is attained by heating the mat immediately prior to its fixing on its support to relieve slightly the binding of the layers of fibers by the thermoplastic material, which gives rise to a re-arrangement of the stratification of fibers adjacent to the surfaces of the underlayer.

9 Claims, 3 Drawing Figures Patented April 25, 1972 3,658,633

2 Sheets-Sheet 1 v INVENTORS (241/05 J/Mewr/ae ATTORNEY AGGREGATES OF MINERAL FIBERS AND THERMOPLASTIC MATERIALS USEFUL PARTICULARLY AS UNDERLAYERS FOR STRUCTURAL SHEATHINGS FOR ACOUSTIC INSULATION The present invention has for its object the production of aggregates or compounds from mineral fibers, particularly glass fibers, and thermoplastic materials, which are designed in particular to be used as underlayers of sheathings which assure acoustic insulation. These sheathings are especially useful for sound-proofing floors and walls.

In accordance with the invention, these products are constituted of mineral fibers, particularly glass fibers, the length of which is at least of the order of the decimeter, and the mean diameter of which is between microns and 40 microns, these fibers being interlaced in parallel planes to form a mat or padding, and joined together by one or several elastomers constituted by natural or artificial latexes to which are, added one or more adjuvants to assure a chemical bridge between the I glass and the elastomers and/or coagulation of the elastomer, the percentage by weight of the binder being between 20 percent and 50 percent relative to the total weight ofthe product.

Advantageously, the weight of the fiber mat may range between 150 to 300 grams per square meter.

It has been established that such products, used as underlayers of sheathings, increased, to a large degree, the acoustic insulation characteristics of these sheathings. It has also been determined that these products preserved their sound-proofing characteristics in spite of significant mechanical influences, which are normally imposed on sheathings, such as shearing stresses, compressions resulting from defects in smoothness of the surface to be covered, etc. In addition, these products, due to the mineral characteristics of their reinforcement, do not decay or decompose, are stable in their dimensions, and are non-flammable to a high degree, i.e., they are difficult to burn.

lt is also the object of the invention to improve the adhesion between the juxtaposed surfaces of underlayers and sheathings when these are glued together, by modifying the contacting surface of the underlayer to prevent the migration of glue to the interior of the latter. This is done by partially or completely clogging the pores at this surface with a compatible mixture of mineral fibers, thermoplastic binder and filler.

Also, the invention aims to improve the esthetic appearance of the combined underlayer and sheathing, especially when the latter is of vinyl plastic, by eliminating the transverse folds in the former, occasioned by the winding thereof on a storage drum, by a controlled heating of the underlayer immediately before the application of the plastic sheathing thereto.

The underlayers constituted by the products in accordance with the invention may be associated with pliable wall or floor coverings or with rigid wall or floor coverings.

l Underlayers for Pliable Wall or Floor Coverings or Sheathings The elastomer or elastomers in the form of aqueous emulsions used for the binder, with their specific agents of reticulation for the formation of a network, are of natural latex or synthetic latexes, more particularly of one of the following groups: polychloroprene, carboxylated butadiene styrene and acrylonitrile butadiene.

The adjuvants'assuring a homogeneous distribution of the elastomers in the fibrous mass during preparation of the underlayers designed for pliable sheathings may be the following:

1. the type conducive to the formation of a chemical bridge between the elastomers and the glass: 0. mercapto-silane, itself already known as a bond in rubber-glass textiles. b. formaldehyde resorcinal resin with acrylic thickener. 2. the type conducive to a physical blocking of the elastomer before and during the removal of water in the drying phase,

a. cellulosic thickener, for example, methyl cellulose, the

viscosity of which increases rapidly with the temperature;

b. in the particular case of neoprene latex, thermo-coagulant by acidification of the sizing, for example: ammonium salts, particularly nitrate, sulfate, chlorate of ammonia.

The percentage of the elastomer or elastomers with adjuvants is between 20 percent and 40 percent by weight, with respect to the total weight of the underlayer in the case of wall sheathings. It is between 35 percent and 50 percent in the case of floor sheathings.

Wall sheathings may be formed, for example, of cloth. paper, etc., the floor sheathings may be of materials such as, for example,polyvinyl chloride, linoxyn, moquette carpet, velvet pile, etc.

The underlayer may be fixed or fastened to the sheathing by its direct formation on the sheathing, or through the intermediary of a glue or adhesive composition, for example, a synthetic resin base dispersed in the water or dissolved in a solvent.

ll Underlayers for Rigid Wall or Floor Coverings or Sheathings The elastomer, with its specific reticulating agent, is constituted by an aqueous emulsion of synthetic latex of the carboxylated butadiene styrene group.

The adjuvant, which assures a homogeneous distribution of the elastomer in the original fibers by physical blocking of the elastomer before and during the removal of water during the drying phase, is constituted by a cellulosic thickener, for example, methyl cellulose, the viscosity of which increases very rapidly with the temperature.

The percentage of the elastomer is between 20 percent and 40 percent by weight with respect to the total weight of the underlayer in the case of wall sheathings and between 35 percentand 50 percent in the case of floor sheathings.

It may be advantageous to subject the surface of the underlayer to a treatment which consists in depositing on the surface of the underlayer coming in contact with the sheathing, a thin layer, such as a film of polyvinyl chloride, a layer of hutadiene styrene resin rich in styrene, an aqueous dispersion of polystyrene, glass muslin (cloth), etc., which permits a better distribution of the localized loads transmitted by the rigid sheathing and thereby reduces the permanent deformations of the assembly.

Wall sheathings may be constituted, for example, by plates of wood, metal, glass-resin aggregates, etc.

Floor sheathings may themselves be constituted by flooring elements in the form of thin wooden sheets, plates of polyvinyl chloride with fillers and hardeners, etc.

The fixing of the underlayer to the sheathing may be attained by means of a glue constituted by a film having a synthetic resin base dispersed in water or dissolved in a solvent, for example, polyvinyl acetate in aqueous dispersion.

In every case, where is involved the matter of producing underlayers for either pliable or rigid sheathings, the mode of fabricating the underlayer may advantageously be as follows:

A homogeneous mixture is made of an elastomer or elastomers with their specific adjuvants. The original fiber is saturated with this mixture by any appropriate procedure, such as by dipping, soaking, or steeping in an immersion bath, or by flooding, by spraying, etc., and the mat of original fibers, thus saturated with elastomer, is dried in any suitable way, by suction, compression, gravity, etc. The dried original fiber is further dried thereafter in the course of the reticulation of the elastomer or elastomers at their specific temperature of reticulation or network formation.

The presence of one or more adjuvants in the elastomer or elastomers, makes possible the prevention of the usually observed phenomenon with this type of binder, that is, a migration of the binder on the two faces of the pad during drying,

this migration causing the heterogeneity or non-uniformity of the final product. In order to improve the action of the adjuvants, it is particularly advantageous tobegin the drying by a rapid heating of the inner layers of the pad, for example, by means of heating by infra-red rays. The end of drying and the reticulation may may be realized by any appropriate means such as infra-red radiation, circulation of hot air, etc.

The annexed drawings portray the mode of practicing the invention herein and the characteristics of the products resulting therefrom,wherein FIG. 1 shows schematically and-by way of example, an apparatus for the formation of underlayersaccording to the invention; and v FIGS. 2 and 3 are graphs portraying the sound-insulation characteristics of the products in accordance therewith.

In FIG. 1, the long fibers I, proceeding from an appropriate production device 2, fall in successive layers onto a wire mesh or perforated conveyor belt 3 which passes over an opentopped casing 4 which is placed under a reduced pressure. The fibers become entangled or interlaced in the parallel planes to form a pad or mat 5. This mat is then brought by a meshed conveyor belt 6 to the sizingstation which comprises a vat 7, wherein is prepared the homogeneous mixture'of the one or more elastomers with their adjuvants, and a distributor 8 from which the mixture flows to impregnate the mat. The mat, impregnated withbinder, then passes onto a meshed conveyor belt 9 to be carried to the drying station which comprises a pressing cylinder 10 and a casing 11 which is placed below the latter and under the belt 9, and to which is connected a pump 12. The dried mat is carried by a conveyor belt 13 under a row of drying heaters 14. of infra-red rays, then into a chamber 15 where reticulation of the elastomer or elastomers is effected. The underlayer thus formed is finally made up at I6;

Two examples of underlayers according to the invention are given below, the first relating to an underlayer for pliable fioor sheathing, and the second to an underlayer for a rigid floor sheathing.

Example 1 (Underlayer for Flexible" Floor Sheathing) The underlayer is obtained from glass fibers some decimetors in length, and of a'mean diameter. of lo-rnicrons, manufactured by a gaseous drawing-out process. The pad or mat obtained has aweight of approximately 220 grams per square meter, and its thickness is about 18 to 10 mm.

The fibers of this mat are linked by means of a binder of the following composition:

Polychloroprene latex emulsion 7.63% Cellulosic thickener 0.l7% Thermocoagulation agent 1 (ammonium sulfate) 0.20% Water 92.00%

10 kg. per cm. of width 2 kg. per square centimeter Resistance to traction: Shearing resistance:

The underlayer is joined to a floor sheathing constituted by I a plasticized and polyvinyl chloride with fillers. The thickness of this sheathing is about 15 to [0 mm. I

- 1 The curve shown in FIG. 2 illustrates the improvement in insulation against shock noisesv as a function of the sound frequency in cycles per second for the aggregate above placed on a, floor or ceiling of'solid reinforced concrete having a thickness of l4 cm. In this graph, the differences of sound levels in decibels, represented as ordinates, are expressed by the relation: A L L L in which L equals the sound level which is picked up when the machine producing the shocks is placed upon the bare floor, without sheathing, and L, equals Example ll (Underlayer for Rigid Floor Sheathing) The pad of fiber glass has the same characteristics as that of Example I.

The fibers of this pad are bound by means of a binder, the composition of which is the following:

Emulsion of carboxylated butadiene styrene latex 7.7% Thermo gelifying thickener 0.3% Water I i 92 .091

The percentage by weight of this binder with respect to the totalweight of the underlayer is 40 percent.

The mechanical characteristics of-the underlayer are as follows: T

16 kg. per cm. of width 3 kg. per square centimeter Resistance to traction: Resistance to shearing:

This underlayer is joined to a floor sheathing constituted by thin wood planks of an area 12.5 cm. X 2.5 cm., and of8 mm. thickness. Adherence of the floor layers on the underlayer is assured by the use of 200 grams per square meter of an aqueous emulsion of polyvinyl acetate. t

The curve shown in FIG. 3 illustrates the improvement in insulation against shock noises as a function of the sound frequency in cycles per second for the aggregate above, used in a laminated floor with an underlayer glued to a solid reenforced concrete floor or ceiling, 14 cm. in thickness.

he improvement index (CSTB), a'= 26"dB, is comprised in this curve. I j

Although in the preceding examples, the application of aggregates according to the invention as underlayers for sheathings of wall or floor'construction, has been envisaged, it should be'understood clearly that these aggregates'can be used either directly or in association with sheathings in the production-of thermal insulation. Also, these aggregates and compounds may be used for other purposes, for example. for heat insulation of vehicles or parts ofvehicles.

The instant invention also seeks to cope with special problems which arise in the course of fabricating the final products of the invention, that is, underlayers associated with rigid-or pliable sheathings, for example, laminated flooring plates, slabs or sheets of vinyl chloride, etc., or applying such underlayers to supports, such as floors or walls.

When a gluing technique is used in these operations, and

particularly when the adhesive which is' used is of light viscosity, it has been determined that the glue migrates in the fibers of the product, which, on the one hand, gives rise to a deterioration of the elastic properties of the product, and on the other hand, for the same quantity of glue being used, results in an impairment or weakening of the .adherence of the fibrous product to the sheathing or to the support.

This fault is overcome by the procedure described below.

In accordance with the invention, the pores of one or both faces of the fibrous product are partially or totally clogged before the application'thereto of the adhesive for affixing the same to the sheathing or other support.

This partial or total clogging of the pores may be realized by depositing on the surface of the fibrous product, in the course of or after its fabrication, a thin layer consisting of a binder, a mineral filler, and mineral or organic material in the form of fibers of small diameter ranging generally between 1 micron and l0 microns.

One may use in particular the following products:

a. Binders such as: an emulsion of polyvinyl acetate, butadiene styrene, vinyl ethylene acetate, bitumen, etc.; phenolformaldehyde resins; milk of starch, etc.

b. Mineral fillers such as: chalk, silica, diatamaceous earth, perlite, etc.

c. Mineral or organic fibers of small diameter ranging between 1 micron and microns.

These products may be handled as follows:

a. The binders may be applied either by spraying or atomizing, by spreading with a scraper blade, or by means of a depositing roller, but in this case the binders must be characterized by a high viscosity ranging between l,000 to 10,000 centipoises. A drying by hot air serves to complete the setting of the aqueous binders.

b. The fillers may be added to the one or more binders, or they may be added by a suitable mechanical projecting apparatus.

c. The fibers may be applied by a suitable projecting device. This operation may be effected advantageously at the same time as the original fibers of the mat are formed.

The quantity of the products which are used, depend upon the degree of clogging of the pores which is desired to be obtained. The usual quantities which are used may range between 5 and 100 grams per square meter, and particularly 10 to 30 grams per square meter deposited in one or more successive layers.

As a non-limiting example, a treatment of the surface which is particularly effective to obtain good adhesion, may be attained with an aqueous solution having the following compositron:

Emulsion of carboxylated This solution is deposited by means of a scraper or depositing roller on the surface of the fibrous product in such a way that after drying and ventilated heating by hot air, the quantity of the solid material which is deposited is about 30 grams per square meter.

The instant invention is also concerned with another problem which arises when the underlayers, as described above, are combined with sheathings of plastic material, particularly vinyl sheathings which are applied to an aggregate of mineral fibers and thermoplastic materials by a coating procedure.

in order to produce this combination, the paste of plastic material, such as vinyl resin, is applied and then hardened on the fibrous product as it advances continuously. The final appearance of the sheathing depends on the condition of the surface of the fibrous product at the moment of its coating.

lf, between the time of its production and that of its use, the fibrous product in accordance with the invention is stocked on drums or rollers, this rolling may cause a partial disarrangement of the initial stratification of the fibers, which becomes evident by the appearance of transverse folds in the surface of the fibrous product. These transverse folds disappear only partially when the fibrous product is unrolled, and these irregular faults in the smoothness of the product are evident as an integral part of the finally coated sheathing, thereby rendering them unacceptable for aesthetic reasons.

This fault is overcome by the inventive procedure described below.

The inventive improvement consists in bringing the fibrous product, before the coating operation, to a temperature such that the thermoplastic binder of the aggregate is softened, thereby to effect a rearrangement of the fibers along the initial planes of Stratification. The transverse folds which are formed in the course of rolling the product disappear completely and the product acquires its initial smoothness.

The heating treatment may be effected on the coating machines immediately before the covering layer is applied, generally by a scraper serving to lay up the vinyl paste onto the fibrous product which is maintained under tension.

During the treating procedure of the surface in accordance with the invention, one may use advantageously: a tension on the fibrous product ranging between 0.5 kg./cm. and 5 kg./cm. of width; a uniform temperature ranging between l20 C. and 170 C., and preferably 160 C.

After this thermal treatment of the fibrous product as it travels continuously, it is not necessary to subject the material to any deformation during the operations of deposition, hardening and then cooling of the vinyl coating.

We claim:

1. An acoustic insulating underlayer in combination with structural sheathing adapted to be affixed with adhesive to a surface of said underlayer, said underlayer comprising a. a reticulated mat of long glass fibers at least approximately a decimeter in length and of a mean diameter ranging from 10 microns to 40 microns,

b. said glass fibers being mutually interlaced in a plurality of parallel planes,

c. a binder for said glass fibers comprising d. at least one elastomer selected from the group consisting of natural and artificial latex, and

e. at least one adjuvant for assuring a chemical bond between the fibers and elastomer component or the coagulation of the elastomer,

f the percentage of the weight of the binder being 20 per-.

cent to 50 percent of the total weight of the product, which ranges in weight between 150 grams to 300 grams per square meter, and in thickness between approximately 10 mm. to 18 mm., said product including a supplemental filling layer of a compatible composition of mineral fibers, thermoplastic binder and mineral fillers, on.at least one surface thereof, for clogging at least partially the pores of said product adjacent to said surface and thereby blocking the migration of said adhesive to the interior of said product, said mineral fibers being of small diameter ranging from 1 to 10 microns and said mineral filler being selected from the group consisting of chalk, silica, diatomaceous earth and perlite.

2. A product as set forth in claim 1 wherein a. the binder of artificial latex is an aqueous emulsion selected from the group consisting of polychloroprene, carboxylated butadiene styrene, and acrylonitrile butadiene, and

b. the adjuvant is selected from the group consisting of mercapto-silane and formaldehyde resorcinal resin with acrylic thickener.

3. A product as set forth in claim 1 including a cellulose thickener which reacts with an aqueous emulsion of the elastomer before and during the removal of the water therefrom to effect a blocking up of the elastomer and the formation of a network thereof amongst the glass fibers.

4. A product as set forth in claim 3 wherein the cellulose thickener is methyl cellulose.

5. A product as set forth in claim 1 wherein the artificial elastomer component is neoprene latex with the adjuvant being a thermo-coagulant ammonium salt selected from the group consisting of ammonium nitrate, ammonium sulfate and ammonium chloride.

6. A product as set forth in claim 1 wherein the binder in said supplemental filling layer is selected from the group consisting of emulsions of polyvinyl acetate, butadiene styrene, vinyl ethylene acetate and bitumen.

7. A product as set forth in claim 1 wherein the filling layer may range in weight from 5 to grams per square meter.

8. A product as set forth in claim 1 wherein the filling layer may range in weight from 10 to 30 grams per square meter.

9. An acoustic insulating underlayer in combination with structural sheathing adapted to be affixed with adhesive to a surface of said underlayer, said underlayer comprising a reticulated mat of long glass fibers at least approximately a decimeter in length and of a mean diameter ranging from 10 microns to 40 microns,

. said glass fibers being mutually interlaced in a plurality of parallel planes,

a binder for said glass fibers comprising at least one elastomer selected from the group consisting of natural and artificial latex,

. at least one adjuvant for assuring a chemical bond between the fibers and elastomer component or the coagulation of the elastomer,

the percentage of the weight of the binder being 20 percent to 50 percent of the total weight of the product, which ranges between 150 grams to 300 grams per square meter,

. a supplemental filling layer on at least the surface of said 

2. A product as set forth in claim 1 wherein a. the binder of artificial latex is an aqueous emulsion selected from the group consisting of polychloroprene, carboxylated butadiene styrene, and acrylonitrile butadiene, and b. the adjuvant is selected from the group consisting of mercapto-silane and formaldehyde resorcinal resin with acrylic thickener.
 3. A product as set forth in claim 1 including a cellulose thickener which reacts with an aqueous emulsion of the elastomer before and during the removal of the water therefrom to effect a blocking up of the elastomer and the formation of a network thereof amongst the glass fibers.
 4. A product as set forth in claim 3 wherein the cellulose thickener is methyl cellulose.
 5. A product as set forth in claim 1 wherein the artificial elastomer component is neoprene latex with the adjuvant being a thermo-coagulant ammonium salt selected from the group consisting of ammonium nitrate, ammonium sulfate and ammonium chloride.
 6. A product as set forth in claim 1 wherein the binder in said supplemental filling layer is selected from the group consisting of emulsions of polyvinyl acetate, butadiene styrene, vinyl ethylene acetate and bitumen.
 7. A product as set forth in claim 1 wherein the filling layer may range in weight from 5 to 100 grams per square meter.
 8. A product as set forth in claim 1 wherein the filling layer may range in weight from 10 to 30 grams per square meter.
 9. An acoustic insulating underlayer in combination with structural sheathing adapted to be affixed with adhesive to a surface of said underlayer, said underlayer comprising a. a reticulated mat of long glass fibers at least approximately a decimeter in length and of a mean diameter ranging from 10 microns to 40 microns, b. said glass fibers being mutually interlaced in a plurality of parallel planes, c. a binder for said glass fibers comprising d. at least one elastomer selected from the group consisting of natural and artificial latex, e. at least one adjuvant for assuring a chemical bond between the fibers and elastomer component or the coagulation of the elastomer, f. the percentage of the weight of the binder being 20 percent to 50 percent of the total weight of the product, which ranges between 150 grams to 300 grams per square meter, g. a supplemental filling layer on at least the surface of said underlayer adjacent to the structural sheathing for preventing the migration of the adhesive to the interior of said underlayer, said filling layer adapted to clog at least partially the pores at said surface, and comprising mineral fibers of small diameter ranging from 1 to 10 microns, a filler of mineral material and a binder therefor consisting essentially of an aqueous solution containing 4 percent of an emulsion of carboxylated butadiene styrene, 2 percent of a cellulosic thickener, 12 percent of chalk, and 82 percent water. 